The running properties of a tire, in particular of a pneumatic tire, do not depend solely on the constitution of the rubber of the tread; the constitutions of the rubber of the individual interior components also affect the running behavior of the tire, and stringent requirements are therefore also placed on the constitution of the rubber mixture at those locations. By way of example, in tubeless pneumatic tires, an inner liner arranged radially in the interior and having maximum impermeability to air prevents air introduced into the tire from escaping, which would result in significantly adverse effect on running behavior. However, for the inner liner to remain airtight, it also has to have good resistance to cracking and to fatigue, in order that driving operations do not produce cracks that impair airtightness. Resistance to cracking, and good abrasion behavior, are also demanded by way of example from the rubber mixture of the sidewall.
A wide variety of attempts have therefore been made to improve the properties of the respective rubber mixtures via the variation of the polymer components, of the fillers, and of the other additives added. A factor that has to be taken into account here is that an improvement in one of the properties often causes impairment of another property. By way of example, an improvement in cracking resistance is generally associated with increased heat accumulation, with poorer abrasion behavior, and also frequently with poorer air permeability.
Rubbers typically used for the inner liner are chlorobutyl rubber or bromobutyl rubber, occasionally blended with natural rubber. These types of rubber have low gas permeability. A further increase in airtightness can be achieved by adding voluminous low-activity or inert fillers and/or fillers with layer structure or platelet structure, but this simultaneously impairs cracking properties and fatigue properties.
Appropriate mention should be made of the following related art publications: DE 100 58 297 A1; DE 100 59 287 B4; U.S. patent application publication 2008/0125537; EP 0 178 079 A1, U.S. Pat. No. 7,491,765; and, U.S. Pat. No. 7,019,603.
DE 100 58 297 A1 and DE 100 59 287 B4 respectively disclose the use of phyllosilicates that have been modified with alkylammonium ions. The corresponding rubber mixtures comprise at least one co-crosslinking agent and feature high elongation at break alongside good modulus and good tear-propagation resistance.
United States patent application publication 2008/0125537 describes a rubber mixture, preferably for the inner liner of pneumatic tires, which comprises from 50 to 100 phr of halobutyl rubber, from 5 to 45 phr of polyisobutylene, and from 10 to 120 phr of carbon black. U.S. patent application publication 2008/0125537 addresses the object of reduced plasticizer diffusion and good compressive and tensile properties of the vulcanisates.
EP 0 178 079 A1 discloses a rubber mixture and a process for producing a rubber mixture, where the mixture comprises natural rubber as rubber component, kaolin and metakaolin and carbon black as fillers, and a quaternary ammonium salt as coupling agent.
U.S. Pat. No. 7,491,765 describes a rubber mixture, in particular for the inner liner of a pneumatic tire, which comprises from 40 to 100 phr of halobutyl rubber, and at most 60 phr of a further rubber, and talc. U.S. Pat. No. 7,491,765 addresses the object of high airtightness and improved resistance to fatigue.
U.S. Pat. No. 7,019,603 discloses a rubber composition for an internal lining of a pneumatic tire, where the lining comprises a clay in platelet form or arranged in layers, and where the rubber layer of the internal lining must have a particular thickness.
The phr (parts per hundred parts of rubber by weight) data used in this specification are the usual quantitative data for mixing specifications in the rubber industry. The amounts added of the parts by weight of the individual substances here is always based on 100 parts by weight of the total mass of all of the rubbers present in the mixture.